(a) Technical Field
The present disclosure relates to a display device and a method of driving the same. More particularly, the present disclosure relates to an organic light emitting device and a method of driving the same.
(b) Discussion of Related Art
A pixel of an organic light emitting device includes an organic light emitting element, along with a thin film transistor (TFT) and a capacitor that drive the light emitting element.
The TFT is classified as a polysilicon TFT or an amorphous silicon TFT, according to the kind of active layer.
Because amorphous silicon is deposited at a low temperature and forms a thin film, the amorphous silicon is generally used for a semiconductor layer of a switching element of a display device that mainly uses glass having a low melting point as a substrate. The amorphous silicon TFT, however, has a difficulty in providing large increases in a display area of a display element due to low electron mobility. Furthermore, because the amorphous silicon TFT continuously applies a DC voltage to a control terminal, a threshold voltage is varied, whereby the amorphous silicon TFT may be degraded. This becomes a major factor that shortens the lifetime of the organic light emitting device.
Therefore, application of a polysilicon TFT that has high electron mobility, good high-frequency operation characteristics, and a low leakage current is desirable. In a process of forming an active layer with polysilicon, however, due to characteristics of a semiconductor that is included in the TFT, it is not easy to uniformly form the polysilicon TFT within the display device. Therefore, a deviation occurs in a threshold voltage and electric field effect mobility of the driving transistors and, thus, screen uniformity is deteriorated.
Furthermore, because a sequential degradation phenomenon may occur in a polysilicon TFT, deviations may sequentially occur in a threshold voltage and electric field effect mobility of driving transistors and, thus, a luminance deviation may occur between pixels.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.